Meredith Kercher, a 21-year-old from Leeds University, was found semi-naked and with her throat cut in a house she shared with American student Amanda Knox in November 2007.
Knox and her Italian ex-boyfriend Raffaele Sollecito were convicted in 2009 of killing Miss Kercher, from Coulsdon, Surrey, but were freed last October after their convictions were overturned on a lack of evidence.
Rudy Guede, a petty criminal and drug dealer from the Ivory Coast, was convicted of sexually assaulting and murdering the student and is serving a 16-year-sentence.
In his book, Honour Bound, which is due out next week, Mr Sollecito maintains the couple’s innocence but acknowledges that their sometimes bizarre behaviour after Miss Kercher’s death gave police reason for suspicion.
He describes how the early days of his relationship with Miss Knox became a nightmare with the horror of Miss Kercher’s death, the misunderstandings that swept them up in the case, and their tabloid portrayals as two suspects unrecognisable to themselves.
Miss Knox became “Foxy Knoxy” and received the brunt of the attention as she shopped for underwear after the killing and turned cartwheels in front of investigators.
While police investigated the crime scene, Mr Sollecito caressed her and they kissed, unaware of the television news cameras across the street.
Later at the police station she climbed in his lap and draped her arms over him, making Sollecito uneasy, he wrote.
Police found their behaviour “odd” and he acknowledged they had no “real alibi the night of November 1 except each other”.
Mr Sollecito, then finishing his undergraduate studies in computer science, wrote about how he met Miss Knox at classical music concert a week before Miss Kercher’s death, and that they became inseparable.
Miss Knox is also writing a book, due out next spring, in a deal reportedly worth £2.5m.